Off road vehicle apparatus and method

ABSTRACT

A ground engaged vehicle includes a front portion and a rear portion joined by an articulation. The articulation rotates around a longitudinal axis. An engine drives a hydrostatic pump which drives four hydrostatic motors, each of the hydrostatic motors in operative engagement with one of four wheels. The wheels are on wheel mounts, each of the wheel mounts having a vertical axis around which one of the four wheels with one of the hydrostatic motors is turnable. A steering system turns the two wheels of the front portion in a first direction and the two wheels of the rear portion in an opposite direction. The steering system is powered by the hydrostatic pump. A pedal control system has a first pedal controlling driving the vehicle in a forward direction and a second pedal controlling driving the vehicle in a rearward direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/999,836 filed on Nov. 30, 2004.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

APPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of this invention is in off road, ground engaged vehicles.

2. Related Art

Non-construction and non-agricultural off road vehicles include variousclasses of designs including what are popularly known as “all terrainvehicles” and “utility vehicles.” These types of off road vehicles facea variety of challenges in covering terrain. Most of these challengesare related to obstacles, objects and/or soft ground in the path oftravel that can stop the vehicle's progress. Meeting and overcomingthese obstacles is more successful to the extent that the followingcharacteristics can be optimized: lowering the center of gravity;increasing power; maintaining traction; maintaining stability;maximizing ground clearance; maximizing maneuverability; and, whennecessary, easing maintenance. As always, controlling cost is acontinuing need in the art.

Most vehicles in the all terrain vehicle (ATV) and utility vehicle (UV)classes have suspensions systems similar to the familiar automobilesuspension systems and constructed and arranged with springs and shockabsorbers and the like. The design of said systems allows an individualwheel to travel vertically relative to the rest of the vehicle in orderto ride over an obstacle while the rest of the vehicle proceeds past theobstacle. The problem with such suspension systems is that the vehiclebody as a whole does not increase its ground clearance when it is mostneeded—when a large obstacle is to be overcome. Hence, when an obstacleis large enough, a sprung wheel may flex vertically to accommodate it,but the ground clearance of the body of the vehicle will still bestopped by the obstacle. There is a need in the art for a vehicle thatwill increase the ground clearance of its entire body in order toovercome larger or rougher obstacles.

Further, during the time that an individual sprung wheel is flexingvertically to avoid an obstacle, traction is lost with that wheel, andthe constant application of power to the ground by that wheel is lost.Hence, there is also a need in the art for an off road vehicle thatcontinues to apply constant traction and power to the ground whileobstacles are overcome.

Prior art ATVs and UVs, having conventional drive systems with themechanical linkages between an internal combustion engine and thewheels, typically including a transmission and differential, furthercomplicating the constant delivery of power and traction to the groundby the wheels in rough terrain. There is a need in the art for a drivesystem that increases power, maintains traction through all four wheelsat all times and affords higher torque in a slower wheel spin.

There is a further need in the art for a vehicle whose maneuverabilityis maximized in order to travel in and through narrow spaces betweeninsurmountable obstacles. Accordingly, there is a need in the art for avehicle with four wheel steering.

Hydrostatic drive and hydrostatic motors mounted directly on the wheelsare known, but not generally in off road vehicles. Skid steers and forktrucks used in warehousing are often driven by hydrostatic motorsmounted directly to individual wheels. The advantage of such drivesystems is very low wheel spin rates and the maintenance of high torqueat extremely low speeds, thereby allowing increased maneuverability inclose quarters, especially while maneuvering a load. It is not known toapply pure hydrostatic drive technology to off road vehicles.Accordingly, there is a need in the art for the maximizedmaneuverability and torque at low speeds afforded by hydrostatic drivesas applied here thereto unapplied to off road vehicle technology.

SUMMARY OF THE INVENTION

It is in view of the above problems that the present invention wasdeveloped. The present invention is an off road vehicle having a frontportion and a rear portion connected by an articulating joint thatrotates around an axis that is longitudinal to the vehicle and parallelto its direction of travel. This articulation allows front and/or rearportions to roll, that is turn about the longitudinal axis, in order tomeet and overcome an obstacle in its path. In so doing, the rollingmotion not only raises the wheel first contacting the obstacle, but alsoraises the front or rear portion of the vehicle, thereby raising thevehicle's ground clearance and allowing it to traverse higher obstaclesthan prior art vehicles.

The articulation system also acts in a manner that allows theelimination of conventional suspension systems. Therefore, all fourwheels are maintained in driving ground contact to a greater extent thanprior art vehicles.

The off road vehicle of the present invention has a hydrostatic drivesystem. A hydrostatic pump is driven by an internal combustion engine. Aflow divider directs the flow of fluid through a hydraulic system inorder to drive each of four hydrostatic motors. In low gear power isdirected to the wheels in diagonal pairs. The four hydrostatic motorsare mounted directly on each of four wheels, one preferred embodimenthaving four wheels.

The present invention has a four wheel steering system. Two wheels aremounted side by side on the front portion of the vehicle. These turn inunison as controlled by a hydraulic piston and cylinder having a two waydrive. A simple lever constructed and arranged with each wheel mountturns each wheel. The levers turn in unison as one of the cylinders orthe piston is connected with each lever. The same system is applied tothe rear portion of the vehicle. However, the front and rear systems arecoordinated such that turning the front wheels in a first directionaffects the turning of the rear wheels in the opposite direction.Thereby, the turning radius of the vehicle is greatly reduced andmaneuverability increased.

The present invention includes a novel wheel mounting system. A verticalpinion is journaled into a solid, non-removable mount fixedly attachedto the body of the vehicle. The wheel and the hydrostatic wheel motorare attached to the bottom of the journaled pinion such that they canturn around a vertical axis. The top of the journal pinion is fixedlyattached to a lever, the other end of the lever being turned by theextension or retraction of one of the piston or cylinder of the steeringlinkage.

The control system of the present invention includes a novel pedalarrangement. Each pedal is constructed to receive a linear motion froman operator's foot. A slotted plate in the body of the vehicle receivesthe linear motion of the pedal shaft, the operation of the pedal isconverted to an angular rotation of the slotted plate. This in turncontrols power delivered to the hydrostatic drive system, and thereforecontrols the speed and progress of the vehicle. The mounted controlsystem of the present invention includes a first pedal for controllingthe vehicle in a forward direction and a second pedal for controllingthe vehicle in a rearward direction.

Further features and advantages of the present invention, as well as thestructure and operation of various embodiments of the present invention,are described in detail below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the embodiments of the present inventionand together with the description, serve to explain the principles ofthe invention. In the drawings:

FIG. 1 is side view of the off road vehicle of the present invention;

FIG. 2 is a perspective view of the off road vehicle;

FIG. 3 is a side view of a wheel mount;

FIG. 4 is a longitudinal view of a wheel mount;

FIG. 5 is a disassembled longitudinal view of the articulation betweenthe front and rear portion in a first position;

FIG. 6 is a disassembled longitudinal view of the articulation betweenthe front and rear portion in a second position;

FIG. 7 is a side view of the articulation;

FIG. 8 is a side view of the inner shaft of the articulation;

FIG. 9 is a schematic diagram of the hydrostatic drive system;

FIG. 9A is a schematic diagram of the hydrostatic drive system in lowgear;

FIG. 9B is a schematic diagram of the hydrostatic drive system in highgear;

FIG. 10 is a schematic depiction of the hydrostatic steering controlsystem;

FIG. 11 is a front view of the pedal assembly;

FIG. 12 is a top view of the pedal assembly;

FIG. 13 is a side view of the pedal assembly;

FIG. 14 is a side view of a pedal;

FIG. 15 is a front view of a pedal assembly actuation disc; and

FIG. 16 is a top view of the vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring to the accompanying drawings in which like reference numbersindicate like elements, the off road vehicle 10 of the present inventionis comprised of a front portion 12 and a rear portion 14. The twoportions are separated by an articulation 60. Two wheels 50 are mountedto the front portion on either side. Two wheels 52 are mounted on therear portion on either side. Each of the four wheels is held in placeand controlled through a mount 40. In the depicted embodiment, an engineand hydrostatic pump are housed in the front section, which includes anexhaust port 18 for the engine. (An intake manifold port is on theopposite side of the vehicle.) The interiors of the front portion 12 andrear portion 14 may be variously configured. In the depicted embodiment,they include seats, the seats having back rests 22 and a control panelhaving a steering wheel 24 in the front portion.

FIG. 2 is a perspective view of the off road vehicle shown encounteringand overcoming an obstacle. As is apparent from FIG. 2, the obstacle isovercome by the articulation between the front portion 12 and the rearportion 14 rolling around its longitudinal axis thereby allowing theright front wheel 50 to elevate over the obstacle. In the process, theentire front portion is correspondingly lifted, thereby increasing itsfunctional ground clearance at the point where it is needed; over theobstacle. Upon the front wheel and front portion descending on the farside of the obstacle, the articulation will allow the front portion torotate back downwards, which would be clockwise in the depictedembodiment. When right rear wheel 52 encounters the same obstacle, thearticulation will allow the rear portion 14 to roll up along thelongitudinal axis of the articulation, which is counterclockwise in thedepicted embodiment, such that right rear wheel 52 may elevate over theobstacle. Of course, rear portion 14 will also be elevated as right rearwheel 52 elevates, thereby increasing its useful center of gravitysimultaneously as well.

Articulation

FIGS. 5, 6, 7 and 8 depict the details of the articulation between thefront portion and the rear portion. The articulation 60 is composed of aforward collar 62 and a rear collar 64. These collars are substantiallyequivalent mirror images of one another. Their inner diameter isthreaded. Each includes a step creating a flange 63 and 65. This flangecorresponds to a through hole provided for it in the back wall hullplate of the front portion 12 and the front wall hull plate of the backportion 14. (In the depicted embodiment, the vehicle is largelyconstructed of welded plate steel.) The rear plate 66 of the frontportion 12 and the front plate 68 of the rear portion 14 appear incutaway side view FIG. 7. Each of the collars 62 and 64 are fixedlyattached to the plates 66 and 68.

Being an off road vehicle, the present invention is designed foroperation in dirty environments. Accordingly, in order for thearticulation to be a durable, low maintenance functional component,novel structure has been created to prevent foreign material such asdirt from degrading its performance. In the depicted embodiment, this isachieved with a bushing or plastic spacer 70. The plastic spacer 70 isdimensioned and constructed to closely cooperate with the hull plates 66and 68.

The center tube 80 of the articulation is threaded on its outsidediameter with threads that correspond to the threaded inside diametersof collars 62 and 64. The axial length of the center tube 80 exceedssomewhat the axial combined depth of the collar 62 and 64 when mountedin place with the plastic spacer 70 and the hull plates 66 and 68. Thethreads of center tube 80 are truncated at their peaks, in order toallow the entire articulation to be greased in order to maintain a waterseal. The center tube 80 (see FIG. 8) includes a hole 82 dimensioned tocorrespond to a hole 84 in one or the other of the collars. In thedepicted embodiment, hole 84 is in the front collar 62. The threadedholes 82 and 84 will receive a bolt for fixedly mounting center tube 80during assembly.

During a fabrication, collar 62 and 64 also have placement or “timing”marks 72 and 74 placed on them. In the depicted embodiment, these marksare machined into the collars. In machining collar 62 and 64, the timingmarks are coordinated with the threads such that screwing the centertube 80 into one of the collars advances the center tube 80 apreconfigured distance in an axial direction.

In assembly of the articulation, each collar 62 and 64 is fixedlyattached to its corresponding hull plates 66 and 68. The timing marks 72and 74 are aligned. Next the center tube 80 is threaded through itscorresponding through hole in plastic sheet 70. An unthreadedcooperation between center tube 80 and plastic sheet 70 remains withinthe scope of the present invention. This assembly is then screwed intothe front collar 62 until hole 82 in center tube 80 is correspondinglyaligned with hole 84 in front collar 62. Thereupon the center tube 80 isfixed in its relation to front collar 62 by screwing a bolt (not shown)through holes 82 and 84. Next the rear hull plate and rear collar 64 arebrought into assembly with center tube 80. Rear collar 64 is screwedinto place. The timing mark of the rear collar 64 is brought intocorrespondence with the timing mark of the front collar 62. Thereafterthe hulls are properly aligned in a neutral and level position and therear collar 64 is fixed to permanently fixedly attach to the rear hullplate 68. Obviously, the order of assembly could be reversed with regardto front and rear without changing the effectiveness of the assembledcomponent or departing from the scope of the present invention. In thedepicted embodiment, since the engine is mounted in the front portion12, the rear portion which will threadingly articulate with the fixedcenter tube 80 through collar 64, will have a grease nipple mounted onit for maintenance.

By carefully aligning the collars and threaded tube between them, theproper preselected tolerance between the outer surfaces of the plasticsheet 70 and the facing surfaces of the rear plate 68 and front plate 66are maintained. Stops may be affixed in any appropriate position betweenthe front and rear portions in order that rotation of the articulationbe controlled. In the depicted embodiment, maximum roll around thelongitudinal axis is 45°. Whether a useable range is thus limited anddefined, or is unlimited in practical use, throughout the range of userotation, the tolerances between the plastic sheet and the hull platesexposed to the contaminated working environment are maintainedacceptably close. In the depicted embodiment, the tolerance ismaintained at a gap of 0.04 inches or less between the plastic sheetsurface and the surface of either plate.

The center tube 80 of the articulation has an inner diameter sufficientto allow passage therethrough of all the necessary hydraulic lines forthe hydrostatic drive system. In the depicted embodiment, this innerdiameter is approximately eight inches.

Mounts

The novel mounting arrangement of the off road vehicle is depicted inFIGS. 3 and 4. The mount assembly 40 is comprised of a mounting plate 42on to which is fixedly attached a substantially vertically orientedcylinder 44. Through this cylinder is journaled a pinion or rod 46 withappropriate bushings, flanges or other mounting devices such that therod 46 does not slide axially through cylinder 44, but may rotate freelywithin it. The rod 46 extends both above and below the extent ofcylinder 44. Below the cylinder, vertical rod 46 is fixedly attached toan angled mounting bracket 48. The wheels 50 or 52 are mounted to thebracket 48 along with a disk brake assembly 54 and a hydrostatic motor56. The hydrostatic motor is powered by hydrostatic system, which isconnected to the hydrostatic motor 56 via hydraulic hoses 57 and 58. Thedisk brakes may be of any conventional design.

As is apparent from the drawings, rotation of the vertical rod 46 willturn the wheels 50, 52. In order to actuate such vertical turning, andthereby actuate steering, the top end of the vertical rod 46 is fixedlyattached to a lever arm 38. At an opposite portion of the lever arm 38from its attachment to the vertical rod 46 is a pivoting attachment 36.The pivoting attachment 36 is connected to a tie rod portion of asteering linkage (not shown). The tie rod extending or retracting turnsthe lever arm 38 and, with it, the vertical rod 46 and wheels 50, 52. Asis more apparent in FIG. 1, the steering linkage is arranged transverseto the direction of travel of the overall vehicle, so that extension andretraction of the linkage would be laterally out from and back intowards the vehicle, which would be in and out of the page in FIG. 1.The steering linkage is described in greater detail below.

As is apparent from FIGS. 3 and 4, there is no conventional suspensionsystem included in the mounting of these wheels. Instead, the action ofthe articulation between the front and rear portion is relied upon toprovide suspension and responsiveness to road obstacles. Additionally,it is the part of the method of use of the apparatus of the presentinvention that tire pressure as used in the tires mounted on wheels 50and 52 be maintained at a low level in order that the tires absorb theshock of smaller obstacles. In the preferred embodiment, six to eightpounds of pressure is maintained in all four wheels. Through thesemechanisms durability is increased and costs reduced.

In one embodiment of this invention, maintenance is further simplifiedby the choice of wheel hubs. The hubs of the depicted embodiment mayreceive mounting of 15 inch wheels. This is a standard size wheel for anautomobile. This is atypical of other ATV and UVs. Accordingly, ifnecessary, a wide range of standard automobile wheels can be used toreplace a flat wheel in the event the off road vehicle is being used ina location inaccessible to more sophisticated maintenance and partsservices.

Hydrostatic Drive System

The hydraulic drive system of the off road vehicle is schematicallyrepresented in FIG. 9. FIG. 9 is a composite schematic of the entiresystem. For clarity, FIG. 9A depicts only the lines in use when thevehicle is in low gear and FIG. 9B depicts only the lines in use and theflow path when the vehicle is in high gear.

The primary components of the hydrostatic drive system are pump 100,flow divider 110, six-way valve 120, and four hydrostatic motors 130,132, 134 and 136, each individually mounted to a wheel. The pump is anOil Gear® brand Model PVWC L51611-672 closed loop variable displacementpump having a maximum capacity of 1.35 cubic inches per revolution and amaximum pressure 4,000 pounds, although in the depicted embodiment arelief valve 3,600 psi installed. The flow divider is a Barnes model060203-1300636. In the depicted embodiment a six-way valve Cross® modelV54 BUBF7 valve is used having 50 gallons per minute capacity. Themaximum capacity of the system is 16 gallons per minute. A novel aspectof this invention is the over size capacity of the six-way valve, whichis used to eliminate any restriction of flow at the valve in order toaccommodate a high gear to be described below and in order to maintain aconstant maximum delivery of power to the wheels in low gear. In placeof a six-way valve, two three way valves may be used instead. Thehydrostatic motors are Parker® model “Gerorotors” having a fixeddisplacement of 20.6 cubic inches and maximum torque of over 20,000 inchpounds. The selected motor is efficient at low flow rates. Othercomponents may be used without departing from the scope of theinvention. The salient characteristics of the components are describedthroughout herein.

The hydrostatic drive system may work in either forward or reverse. Eachdirection of travel will have a high gear and a low gear. When in aforward mode, the pump causes a direction of flow in a forward directionby hydraulic oil leaving port 102 and re-entering the pump at port 104.In order to operate in the reverse direction, the entire flow path isreversed, with hydraulic oil leaving the pump at port 104 and returningat port 102. Hence, all the capabilities of the high and low gearavailable in the forward drive mode are also available in a reversedrive mode.

The pump is driven by an internal combustion engine. In the depictedembodiment, this engine is a 27 hp Kohler model PA-CH740-0012.

The flow divider 110 has an intake port 112 and two output ports 114 and116. Its internal configuration is known. It is a geared flow divider,causing an equal volume of fluid to exit both ports 114 and 116simultaneously in at an equal flow rate.

The six-way valve 120 has two intake ports 121 and 124. It has fouroutput ports 122, 123, 125 and 126. It has two working positions. Onecauses fluid to exit the valve at exit ports 122 and 125. In thisposition exit ports 123 and 126 are closed. In the second workingposition, fluid is output by the valve at ports 123 and 126, and outputports 122 and 125 are closed. In the depicted embodiment, the firstposition of the valve is used for low gear and a second position forhigh gear. The first position for low gear directs fluid flow throughthe flow divider and thereafter directs fluid flow in a novel pathdesigned for the off road utility of this vehicle. In high gear, thesecond position of the six-way valve 120 is used and fluid follows aflow path that does not include the flow divider 110.

Constant power is delivered to all four wheels at all times by virtue ofthe fact that this is a hydrostatic drive system, and also by virtue ofthe fact that there is no slip clutch or differential in the drivesystem. However, the flow path further supplements power delivery bydiagonally pairing the wheels, insuring power to the wheels having themost useful contact with the ground.

In the majority of circumstances, the off road vehicle will encounterobstacles in an asymmetrical fashion. That is, the single forward wheelwill ride over an obstacle while the opposite forward wheel does notneed to ride over the obstacle. Because of the use of the centerarticulation as a suspension system, in the majority of cases as one orthe other front wheel rides over an obstacle, the other front wheel andthe rear wheels will remain relatively flat on the ground and in gooddriving contact with it. After the vehicle has traversed the obstaclewith its front wheel, the same side rear wheel will, in most cases, alsoride over the obstacle. As this happens, the other rear wheel and thetwo front wheels will be in relatively flat and stable contact with theground and in good driving engagement with it. Another relevantsituation is both wheels on one side being on soft or slippery ground,like ice. In low gear, the hydrostatic drive system of the off roadvehicle directs power to the wheels in diagonal pairs. This is done tomaximize the delivery of useful power to the wheels as obstacles aretraversed.

FIG. 9A depicts the flow path in low gear. Pressurized fluid leaves pump100 through a first connected hydraulic hose 140. This fluid is directedinto intake port 121 in six-way valve 120. In the valve's firstposition, this fluid is directed outwards through port 122 into andthrough hose 142 which carries the pressurized fluid flow into port 112of flow divider 110. The flow divider 110 then directs the fluid out inequal volumes from its exit ports 114 and 116. From exit port 114, hose144 transports pressurized fluid to a third wheel motor 134, and drivesit. Thereafter, the fluid exits motor 134 and via hose 148 is directedto second motor 132. Hence motors 134 and 132 are a diagonal pair. Afterentering and driving second motor 132, this fluid is directed via hose150 back to receiving port 104 and the pump 100.

The other diagonal pair of motors, 130 and 136 are driven with thepressurized fluid flow exiting the exit port 116 of flow divider 110.This is first through hose 146, which enters first motor 130. After thefluid has entered and driven first motor 130, it exits motor 130 throughhose 152 and is transported to the diagonally paired fourth motor 136and the fluid drives that motor. Thereafter the fluid exits motor 136through hose 154 and reenters six-way valve 120 at intake port 124. Thisfluid is then directed out exit port 125 into hose 156 which alsodirects the fluid to return port 104 and pump 100. This may be through ajunction with hose 150, or by entering the receiving port 104individually.

It will be noted that hoses 148, 146, 150 and 152 traverse from thefront portion 12 to the rear portion 14 of the vehicle. These hoses aredirected through center tube 80 of the articulation 60.

FIG. 9B depicts the flow path of pressurized hydraulic fluid for highgear. High gear eliminates the flow divider from the flow path. Highgear is of course typified by travel at higher speeds where the vehicledoes not need to traverse substantial obstacles. High gear has a greaterflow through of fluid, without the same high demands for torque to thewheels, and therefore without the demand for divided pressurization ofthe fluid and also the demand for diagonal pairing. Accordingly, flow isdirected in high gear first to motor 130 then to fourth motor 136, thenacross to third motor 134 and finally to second motor 132 beforereturning to the pump 100. More particularly, pressurized fluid isdirected again through hose 140 into intake port 121 of six-way valve120. Thereafter, however, the six-way valve 120 being in a secondposition, the fluid exits exit port 123 of the six-way valve where itproceeds along hose 158. In the depicted embodiment, hose 158 mergeswith hose 146 to transport fluid to first motor 130. Hose 158 mayalternatively be directed independently to first motor 130. Thereafter,hose 152 directs fluid flow, as before, to the fourth motor 136.Thereafter, hose 154 directs fluid to intake port 124 of the six-wayvalve. The six-way valve being in the second position, this fluid isdirected out of exit port 126 where upon hose 160 transports thepressurized fluid to the third motor 134, driving it. Thereafter, asbefore, hose 148 carries the pressurized fluid to the second motor 132driving it. Finally, hose 150 returns the pressurized fluid from secondmotor 132 to receiving port 104 of pump 100.

When the hydrostatic drive system is in high gear, lines usedexclusively for low gear, for example lines 142 and 144 to and from theflow divider, obtain a plenum volume of fluid that remains idle.Similarly, when in low gear, lines dedicated to use in high gear, suchas lines 158 and 160 also retain idle fluid. This fluid does notinterfere with the flow of fluid through the lines being used for thegear selected.

The hydrostatic drive system in the depicted embodiment shifts from lowto high gear and back with a user operated manual switch on thedashboard. The switch controls the six way valve, and moves it betweenits first and second positions.

Steering System

The steering system of the off road vehicle relies on a novel trapped,separate and complementary fluid volume in order to coordinate fourwheel steering. As indicated in FIGS. 3 and 4, a lever arm turns thevertical rods 46 and thereby turns the wheels. The lever arms 38 areconnected 36 with a tie rod. A first tie rod is pivotably connected tothe right rear wheel lever at a first end and is also pivotablyconnected to the left rear wheel lever at an equivalent pivot at the tierod's other end. Similarly, a second tie rod with pivoting connectionsat both ends connects the steering levers of the two front wheels.Intermediate its two ends, each tie rod is connected to a piston rod. Afront piston rod is driven a first direction, right or left in frontwhen the steering wheel is turned, and through the steering systemherein described, the rear tie rod is turned in the opposite directionleft or right simultaneously.

FIG. 10 is a schematic representation of the steering system. As iscommercially available, the main pump 100 includes a charge pump 200that may also be used an implement pump. The steering system is aseparate hydraulic system with a maximum pressure of 1,000 psi and amaximum flow rate of 3½ gallons per minute. For use by the steeringsystem, the charge pump 200 withdraws fluid from the reservoir202/cooler 204 assembly and directs it to a power steering pump/valve.In the depicted embodiment, the power steering pump/valve is a SaurDanfoss® Model OHV-25. Power steering pump/valve 206 when activated byan electrical signal received in the steering wheel that the steeringwheel is being turned, directs the flow of pressurized fluid throughhose 208 to a first cylinder and piston assembly 210. The assembly 210is comprised of a cylinder 212 in which a piston 214 travels axially. Apiston rod 216 is attached to the piston and exits cylinder 212 througha sealed through hole. The piston 214 defines a first piston side space218 and second rod side space 220. Similarly, second cylinder 232encloses a second piston 234, thereby defining a second piston sidespace 238 and second rod side space 240. The ends of piston rods 216 and236 are attached to tie rods 242 and 244, which are in turn linked tothe wheel turn levers 38 as previously described.

The steering system uses a separate sealed fluid volume trapped in firstpiston side space 218 and second piston side space 238, which are joinedby hydraulic hose 246 (which also travels through the center tube 80 ofthe articulation 60). This trapped fluid volume will coordinate theturning of the rear wheels in a direction complementary with the turningof the front wheels, that is to say, in opposite directions.

As pressurized fluid enters the first cylinder assembly 210 from hose208, into first rod side space 220, that space expands, driving piston214 in a first direction, which is upwards in FIG. 10. This will ofcourse have the effect of drawing piston rod 216 and its attached tierod 242 in the first direction. As previously described, this will turnone pair of wheels, for example the front wheels, in a first direction.The driven and pressurized movement of piston 214 will reduce firstpiston side space 218 and thereby pressurize the oil in it. Since oildoes not appreciably compress, this oil will escape 218 through hose246. Thereafter the same trapped fluid will enter the second piston sidespace 238, and thereby pressurize it to the same extent that first rodside space 220 was pressurized. The pressurization of second piston sidespace 238 will drive second piston 234 in a direction opposite thetravel of the first piston 214, which is downwards in FIG. 10. This ofcourse will also drive piston rod 236 and its connected tie rod 244,thereby turning the opposite set of wheels, for example the rear wheels.As is apparent from FIG. 10, the direction of turning of the second rearset of wheels will be opposite the direction of the turning first frontset of wheels. Thereby, four wheel steering is achieved and the turningradius greatly reduced, increasing the maneuverability of the off roadvehicle. Finally, preexisting fluid residing in second side 240 will beexhausted into hose 248 and returned by it to power steering pump/valve206. Finally return line 250 returns used fluid to the main pump. Inorder to turn the vehicle in the other direction, the power steeringpump/valve 206 simply redirects the flow of fluid, so that fluid flowsoutwards from the pump/valve 206 into hose 248, causing the system towork in reverse.

Pedal Assembly

Control of forward and reverse motion of the off road vehicle is througha novel pedal assembly system. The hydrostatic drive is controlled byknown linkages to pump 100. In the depicted embodiment, these arecables. The cables are manipulated in a novel way by pedal assembly 300,see FIGS. 11-15. The engine rpm is controlled by a hand throttle on thecontrol panel.

The forward and reverse linkages are connected to pedal system with disc320, and in particular at ears 322 and 324. Raising one ear engageseither a forward or reverse actuation of the hydrostatic system byplacing traction on the connected cable, which progresses toward thepump in a direction downwardly oriented in FIGS. 11 and 15. Raisingeither ear is by rotating the disc 320 about its central axis 326.Accordingly, raising one ear correspondingly lowers the opposite ear.The disc 320 is centrally mounted with a pivot pin 328 inserted througha throughhole in its central axis 326. The pin 328 is thereafter mountedon bracket 330. Bracket 330 is variously constructed for mounting on theinterior of the front portion 12 of the off road vehicle. The disc 320is rotated by selective use of one of two pedals 340F and 340R. Each ofthese substantially similar pedals is constructed with an arm 342surmounted with a foot pedal 344 designed to be engaged by a user'sfoot. The pedal 340 turns around a pivot point 346. Radially arrangedaround the pivot axis 346 are a series of gear teeth 348. The teeth 348are dimensioned to enter engaged holes 350 in disc 320 which areradially arranged around the center axis 326 of disc 320, and speciallyshaped for maintaining constant contact with teeth 348.

Each pedal 340 is assembled with the pedal assembly 300 by pivotablymounting it on a bracket extension 332 using a mounting bolt 334 (notshown). Hence, either pedal when rotating around its pivot axis 346 willconsequently rotate the teeth 348. The teeth 348 being engaged withholes 350 of disc 320, moving either pedal will also turn disc 320. Asis apparent from the figures, depressing right hand pedal 340F willcause disc 320 to rotate in a counterclockwise direction (as seen inFIGS. 11 and 15) thereby causing ear 324 to raise, which will applytraction to the cable attached to it, actuating forward motion. Furtherdepression of the pedal actuates a greater degree of pressure and flowthrough in the hydrostatic drive systems. Since both the forward and thereverse right and left pedals 340 remain in constant engagement withholes 350 of disc 320, depressing one and rotating the disk will havethe corresponding effect of raising the other pedal. This of course putsthe other pedal in a raised position, to ready receive depressing forcefrom the user's foot in order to actuate the opposite direction oftravel.

An extra bracket 360 comprises a lever designed to work in conjunctionwith a pin 362 that inserts in hole 364 in the pedals to act as alocking pin when the vehicle is not in use to prevent inadvertentactuation of motion while the vehicle is idling.

Each hole 350 has a novel “hour glass” shape. The long sides of eachhole, that is the sides that are radial to the center of the disc 320,are convex inwards. In this fashion, teeth 348 that are oblique to therotational axis of the disc, as best seen in FIG. 13, remain in contactwith the sides 352 of their corresponding holes. Thereby, a constant andsmooth mechanical transition of force is achieved, producing desirableeffects in terms of wear, durability and feel to the user. As can beseen in FIG. 13, in normal use one tooth 348 will be usually insubstantially complete and substantially perpendicular engagement withone hole 350, while the two adjacent teeth are engaged in the twoadjacent holes in a more oblique fashion.

Cooling Ports

The engine of the off road vehicle is an air cooled 27 hp Kohler engine.FIG. 16 is a top view of the off road vehicle. The engine andhydrostatic drive system are beneath the seats in the front portion 12of the vehicle. In FIG. 16, the seat has been treated as if it weretransparent in order to show the position of the components beneath it.Those components include the engine 400 and intake cooling fan 402. Theengine is operatively connected to the pump 100 which in turn drives thehydrostatic lines, of which only one is shown, 140, for clarity. Theengine has an exhaust 404 which terminates in a driver's side exhaustport 420.

In order to properly cool the engine and achieve a proper air flow overthe air cooled engine, a porting system has been designed as follows.The intake 418 allows air to be drawn into the engine compartment by fan402, as is indicated by the arrow 406. The fan 402 blows the cooling airover the engine 400 and onwards into the engine compartment. Some of theair will be released through opposing duct 420. However, this duct isalso occupied by the muffler 404. Accordingly, opposing duct 420 isconstricted relative to the intake duct 406. This may lead to reducedair flow and retention of heated air, creating an overheating risk inthe enclosed engine compartment. Accordingly, an additional air exhaustport 430 has been fabricated into the engine compartment behind the seatused by the driver and passenger. Air exits this exhaust port 430 asindicated by the arrow 408, thereby providing adequate relief venting ofheated air from the engine compartment.

In view of the foregoing, it will be seen that the several advantages ofthe invention are achieved and attained.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated.

As various modifications could be made in the constructions and methodsherein described and illustrated without departing from the scope of theinvention, it is intended that all matter contained in the foregoingdescription or shown in the accompanying drawings shall be interpretedas illustrative rather than limiting. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims appended hereto and their equivalents.

1. A ground engaged vehicle comprising: a front portion; a rear portion;said front and rear portion being joined by an articulation, saidarticulation rotating around a longitudinal axis; an engine, said enginebeing mounted in one of said front or said rear portions, said enginebeing in operative engagement with a hydrostatic pump; four wheels; fourhydrostatic motors, each of said hydrostatic motors in operativeengagement with one of said four wheels; four wheel mounts, each of saidwheel mounts having a vertical axis around which one of said four wheelswith one of said hydrostatic motors is turnable; two of said wheelmounts mounting two of said four wheels and two of said four hydrostaticmotors on said front portion and two of said wheel mounts mounting twoof said four wheels and two of said four hydrostatic motors on said rearportion; a hydrostatic drive system in operative engagement with saidhydrostatic pump and with each of said hydrostatic motors; a steeringsystem to turn said two wheels of said front portion in a firstdirection and said two wheels of said rear portion in an oppositedirection, said steering system being powered by said hydrostatic pump;and a pedal control system having a first pedal controlling driving thevehicle in a forward direction and a second pedal controlling drivingthe vehicle in a rearward direction.
 2. A ground engaged vehiclecomprising: a wheeled front portion; a wheeled rear portion; ahydrostatic drive system driving at least one of said wheeled front andrear portions; and an articulation between said wheeled front portionand said wheeled rear portion, said articulation allowing said wheeledfront portion and said wheeled rear portion to roll relative to oneanother around a longitudinal axis of the vehicle, wherein saidarticulation is comprised of a first collar attached to said frontwheeled portion and a second collar attached to said wheeled rearportion in a center tube operatively engaged with each of said collars.3. (canceled)
 4. The vehicle of claim 2 wherein said center tube isthreaded and fixed to one of said first or second collars wherein saidrolling is by threaded engagement and rotation around said threadedengagement between the other of said first or second collars and saidcenter tube.
 5. The vehicle of claim 2 further comprising a plasticspacer between said wheeled front portion and said wheeled rear portion.6. The vehicle of claim 5 wherein said wheeled front portion has a rearhull plate engaged in close cooperation with a front surface of saidplastic spacer and said wheeled rear portion has a front hull plateengaged in close cooperation with a rear surface of said plastic spacer.7. The vehicle of claim 6 wherein said close cooperation defines a spaceof less than 0.1 inches. 8-9. (canceled)
 10. The vehicle of claim 4wherein said threaded engagement is comprised of truncated threads. 11.The vehicle of claim 2 wherein an alignment of said first collar, saidsecond collar and said center tube is aligned with the use of a firsttiming mark and a second timing mark, said first timing mark being onsaid first collar and said second timing mark being on said secondcollar.
 12. A ground engaged vehicle comprising: a front portion, a rearportion, said front and rear portion being joined by an articulation,said articulation rotating around a longitudinal axis of said vehicle; ahydrostatic drive system driving at least two wheels; at least twowheels being mounted on one of said front portion or said rear portionand at least one other wheel being mounted on the other of said frontportion or said rear portion; and each of said wheels being mountedwithout suspension.
 13. The vehicle of claim 12 wherein each of saidwheel mounts is comprised of: a vertical cylinder fixedly mounted to oneof said front portion or said rear portion; a vertical rod journaledinto said cylinder such that said rod may rotate within said cylinderaround a vertical axis; and a wheel mounting bracket fixedly attached tosaid vertical rod and adapted for receiving a wheel mounting.
 14. Thevehicle of claim 12 wherein said wheel mount includes a bracket, saidbracket being adapted for mounting a hydrostatic drive motor such thatsaid hydrostatic drive motor is in driving operative engagement with awheel mounted on said wheel mount.
 15. The vehicle of claim 12 whereinsaid wheel mounts are further adapted for mounting disc brakes.
 16. Thevehicle of claim 12 wherein said mount includes a vertical rod mountedto rotate around a vertical axis, and a lever arm fixedly attached to atop end of said vertical rod and adapted for pivoting engagement with asteering linkage.
 17. The vehicle of claim 12 further comprising 15 inchwheels being mounted on said wheel brackets.
 18. The vehicle of claim 12further comprising tires mounted on wheels mounted on said wheel mounts,said tires being adapted to operate with less than 10 pounds psi ofpressure therein. 19-31. (canceled)
 32. A ground engaged vehiclecomprising: a front portion having two wheels; a rear portion having twowheels; an articulation between said front portion and said rearportion, said articulation allowing said front portion and said rearportion to rotate relative to one another around an axis longitudinal tothe vehicle; a hydrostatic drive system; and each of said four wheelsbeing steerable.
 33. The vehicle of claim 32 wherein said two wheels onsaid front portion are steerable by a front steering linkage and saidsecond two wheels on said rear portion are steerable by a rear steeringlinkage; wherein said front steering linkage and said rear steeringlinkage are coordinated by a hydrostatic powering steering system. 34.The vehicle of claim 32 wherein when said front two wheels on said frontportion turn in a first direction, said rear two wheels on said rearportion turn in an opposite direction.
 35. The vehicle of claim 32wherein said front steering linkage for said two wheels on said frontportion is coordinated with said rear steering linkage for said twowheels on said rear portion by a trapped a fluid volume. 36-37.(canceled)
 38. The vehicle of claim 32 wherein said power steeringsystem is driven through a charge pump.
 39. A ground engaged vehiclecomprising: a front portion; a rear portion; an articulation betweensaid front portion and said rear portion, said articulation allowingsaid front portion and said rear portion to rotate relative to oneanother around an axis longitudinal to said vehicle; a hydrostatic drivesystem powering at least two wheels on one of said front or rear portionand at least one wheel on the other of said front or rear portion; saidhydrostatic drive system having a forward direction and a reardirection, each of said forward and rear directions being powered bysaid hydrostatic drive system; and a pedal assembly having a first pedaland a second pedal wherein depression of said first pedal drives saidvehicle in a forward direction and depression of a second pedal drivessaid vehicle in a rearward direction.
 40. The vehicle of claim 39wherein said pedal assembly includes a lever, a first side of said leverbeing operatively connected to a forward drive control of saidhydrostatic drive system and a second end of said lever beingoperatively connected to a rearward drive of said hydrostatic drivesystem.
 41. The vehicle of claim 39 wherein said lever arm of said pedalassembly is a disc rotating around an axis, said disc having a first earand a second ear, said ears also rotating around said axis, saidrotation of said ears around said axis comprising said lever.
 42. Thevehicle of claim 39 wherein said pedal assembly is comprised of teeth onone of said pedals or said disc and slots on the other of said pedals orsaid disc.
 43. The vehicle of claim 42 wherein said teeth of each ofsaid pedals are on an arched surface.
 44. The vehicle of claim 39wherein said pedal assembly is configured such that said pedals rotatearound an axis that is perpendicular to an axis of rotation of saidlever.
 45. The vehicle of claim 42 wherein said teeth on said pedalsengage said slots in said disc, each of said slots being configured suchthat the sides of said slots receiving pressure from said teeth of saidpedals are convex inwards.
 46. The vehicle of claim 39 wherein saidpedal assembly further comprises a locking pin.
 47. (canceled)